Planetary gear device

ABSTRACT

A planetary gear device includes a first, a second, and a third ring-shaped member that are concentrically arranged in that order from the inside. A sun gear is coaxially fixed to an end surface of the first ring-shaped member, planet shafts of planet gears are supported on an end surface of the ring-shaped member, and an internal gear is coaxially fixed to an end surface of the third ring-shaped member. A first cross roller bearing is formed between the first and second ring-shaped members and a second cross roller bearing is formed between the second and third ring-shaped members. Each member is arranged concentrically on a plane that is perpendicular to the device axis, so that a planetary gear device that is extremely slim in the device axial direction can be realized. Since the respective gear parts can be accessed from both sides in the device axial direction, the input and output can be laid out with great freedom.

TECHNICAL FIELD

The present invention relates to a small, compact planetary gear deviceand in particular to a planetary gear device with reduced thickness inthe device axial direction.

RELATED ART

A conventional planetary gear device is composed of a reductionmechanism for reducing the speed of an input high-speed rotation and abearing for rotatably supporting a reduced-speed rotation output memberthat outputs the rotation whose speed is reduced by the reductionmechanism. The reduction mechanism and the bearing are disposedcoaxially along the device axial direction.

However, the above structure is not suited to constituting a flatplanetary gear device with reduced thickness in the direction of thedevice axis.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a planetary geardevice with minimal thickness in the device axial directions.

To achieve the above and other objects, a planetary gear device of thepresent invention includes: a first member that has a ring shape orcolumnar shape and has a circular outer circumferential surface; asecond ring-shaped member disposed concentrically so as to surround thecircular outer circumferential surface of the first member; a thirdring-shaped member disposed concentrically so as to surround a circularouter circumferential surface of the second ring-shaped member; aninternal gear that is coaxially attached to one ring-shaped end surfaceof the third ring-shaped member; a sun gear that is coaxially attachedto an end surface, which is columnar or ring-shaped, of the firstmember; a plurality of planet gears that are attached to a ring-shapedend surface of the second ring-shaped member and engage with theinternal gear and with the sun gear; a first bearing formed between thecircular outer circumferential surface of the first member and acircular inner circumferential surface of the second ring-shaped member;and a second bearing formed between a circular outer circumferentialsurface of the second ring-shaped member and a circular innercircumferential surface of the third ring-shaped member.

Here, it is preferable for at least one of the first bearing and thesecond bearing to be a cross roller bearing.

In a planetary gear device having the above structure, the sun gear, theplanet gears, and the internal gear are supported by the first member,the second ring-shaped member and the third ring-shaped member that arearranged concentrically on a single plane perpendicular to the deviceaxis. Two bearings, for example, cross roller bearings, areconcentrically formed between these members. Accordingly, it is possibleto realize a structure where a reduction mechanism part, which iscomposed of the sun gear, the planet gears and the internal gear, andtwo bearings for supporting these components rotate relative to oneanother, are concentrically arranged on a plane perpendicular to thedevice axis. As a result, a planetary gear device that is extremely slimin the device axial direction can be realized. By using hollow parts asthe sun gear and the first member that are located on the very inside, ahollow-type planetary gear device can also be realized easily.

In order to reduce the number of components and make the device smaller,more compact, and less expensive, it is preferable to form the firstmember and the sun gear from a single member having a ring shape orcolumnar shape, to form an inner ring-side raceway groove of the firstbearing in an outer circumferential surface part of a circular outercircumferential surface of the single member on one side in a deviceaxial direction, and to form external teeth that compose the sun gear inan outer circumferential surface part on another side of the singlemember.

For the same object, it is preferable to form the third ring-shapedmember and the internal gear from a single ring-shaped member, to forman outer ring-side raceway groove of the second bearing in an innercircumferential surface part of a circular inner circumferential surfaceof the single ring-shaped member on one side in the device axialdirection, and to form internal teeth that compose the internal gear inan inner circumferential surface part on another side of the singlering-shaped member.

A scissors-type backlash adjusting mechanism can be attached to theplanetary gear device of the present invention in the following way.Namely, the planetary gear device may further include a fourthring-shaped member that supports the planet gears from an opposite sideto the second ring-shaped member in the device axial direction, whereinthe planet gears include four planet gears that are disposed atintervals of an equal angle, and planet shafts of two planet gears thatare disposed at an interval of 180 degrees are supported between thesecond ring-shaped member and the fourth ring-shaped member so that anangular position in a circumferential direction relative to planetshafts of two other planet gears that are also disposed at an intervalof 180 degrees, can be adjusted.

The following construction may be used to produce a multi-stageplanetary gear device, such as a two-stage planetary gear device.

This is to say, a two-stage planetary gear device according to thepresent invention has the above-mentioned structure, and wherein thefirst member and the sun gear are ring-shaped members, a fifth memberhaving a circular outer circumferential surface is concentricallydisposed inside a circular inner circumferential surface of the firstmember, a front stage-side internal gear is formed in a circular innercircumferential surface of the sun gear, a front stage-side sun gear iscoaxially attached to one end surface of the fifth member in the deviceaxial direction, a plurality of front stage-side planet gears engagedwith the front stage-side internal gear and with the front stage-sidesun gear are disposed between the front stage-side internal gear and thefront stage-side sun gear, and a third bearing is formed between thecircular outer circumferential surface of the fifth member and thecircular inner circumferential surface of the first member.

In the above case also, it is preferable for the third bearing to be across roller bearing.

In an planetary gear device of the above construction, the planetarygear mechanism of the front stage side is also constructed on the sameplane that is perpendicular to the device axis, so that the entireconstruction is extremely slim in the device axial direction.

In this case, the number of components can be reduced by coaxiallyattaching a central rotational shaft to another end surface of the fifthmember in the device axial direction.

In order to further decrease the number of components, it is alsopreferable to form the fifth member, the central rotational shaft, andthe front stage-side sun gear from a single member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C and 1D are respectively a cross-sectional view, a leftend view, a right end view, and a second cross-sectional view alone line1D showing a planetary gear device according to a first embodiment ofthe present invention.

FIGS. 2A, 2B and 2C are respectively a cross-sectional view, a left endview, and a right end view showing a modified embodiment of theplanetary gear device of FIGS. 1A to 1D.

FIGS. 3A, 3B and 3C are respectively a cross-sectional view, a left endview, and a right end view showing a two-stage planetary gear deviceaccording to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a second modified embodiment ofthe planetary gear device of FIGS. 1A to 1D.

FIG. 5 is a cross-sectional view showing a modified second embodiment ofthe planetary gear device of FIGS. 3A to 3D.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

With reference to the attached drawings, there will be describedembodiments of a planetary gear device according to the presentinvention.

First Embodiment

FIGS. 1A, 1B and 1C are a cross-sectional view, a left end view, and aright end view showing a planetary gear device according to a firstembodiment of the present invention. As shown in these drawings, aplanetary gear device 1 of the present embodiment includes a firstring-shaped member 10, a second ring-shaped member 20 disposedconcentrically around a device axis 1 a so as to surround a circularouter circumferential surface 11 of the first ring-shaped member 10, anda third ring-shaped member 30 disposed concentrically so as to surrounda circular outer circumferential surface 21 of the second ring-shapedmember 20.

An internal gear 2 is coaxially fastened onto a ring-shaped end surface32 of the outermost third ring-shaped member 30 by fixing bolts 3. Onthe same side of the planetary gear device 1, a cylindrical sun gear 4is also coaxially fastened onto a ring-shaped end surface 12 of thefirst ring-shaped member 10 by fixing bolts 5. Between the internal gear2 and the sun gear 4, a plurality (in the illustrated example, four) ofplanet gears 6-1 to 6-4 are disposed so as to mesh with the internalgear 2 and the sun gear 4. These planet gears 6-1 to 6-4 are supportedrotatably on planet shafts 61 to 64, respectively, these planet shaftsbeen attached to a ring-shaped end surface 22 of the second ring-shapedmember 20 that functions as a carrier.

Here, a first cross roller bearing 40 is formed between a circular innercircumferential surface 23 of the second-ring-shaped member 20 and thecircular outer circumferential surface 11 of the first ring-shapedmember 10 on the very inside. A second cross roller bearing 50 is formedbetween the circular outer circumferential surface 21 of the secondring-shaped member 20 and the circular inner circumferential surface 33of the third ring-shaped member 30. Accordingly, these first and secondcross roller bearings 40, 50 are formed concentrically about the deviceaxis 1 a.

It should be noted that ball bearings or ordinary roller bearings may beused in place of the first cross roller bearing 40 and/or the secondcross roller bearing 50.

The first cross roller bearing 40 includes an inner ring-side racewaygroove 41 that is formed in the circular outer circumferential surface11 of the first ring-shaped member 10, an outer ring-side raceway groove42 that is formed in the circular inner circumferential surface 23 ofthe second ring-shaped member 20 that functions as a carrier, and aplurality of rollers 43 that are inserted into a ring-shaped racewayformed between the circular outer circumferential surface 11 and thecircular inner circumferential surface 23 so that the rotational axes ofalternating rollers are perpendicular to one another. In the same way,the second cross roller bearing 50 includes an inner ring-side racewaygroove 51 that is formed in the circular outer circumferential surface21 of the second ring-shaped member 20 that functions as a carrier, anouter ring-side raceway groove 52 that is formed in the circular innercircumferential surface 33 of the third ring-shaped member 30, and aplurality of rollers 53 that are inserted into a ring-shaped racewayformed between the circular outer circumferential surface 21 and thecircular inner circumferential surface 33 so that the rotational axes ofalternating rollers are perpendicular to one another.

The planetary gear device 1 of the present embodiment includes ascissors-type backlash adjusting mechanism to adjust the backlash in theengagement of the respective gears. The backlash adjusting mechanism inthe present embodiment includes a fourth ring-shaped member 60 thatsupports the planet gears from the opposite side in the device axialdirection 1 a with respect to the second ring-shaped member 20 thatfunctions as a carrier. The planet shafts 61, 63 (only the planet shaft61 is shown in FIG. 1A) of two planet gears 6-1, 6-3 that are disposedat an interval of 180 degrees are attached between the second and fourthring-shaped members 20, 60 so that it is possible to adjust the relativeangular position in the circumferential direction between these planetshafts 61, 63 and the planet shafts 62, 64 (only the planet shaft 62 isshown in FIG. 1A) of the remaining two planet gears 6-2, 6-4 that arealso disposed at an interval of 180 degrees.

More specifically, at one end, the planet shafts 61, 63 of the twoplanet gears 6-1, 6-3 are fitted into the ring-shaped end surface 22 ofthe second ring-shaped member 20 that functions as a carrier, while atthe other end, the planet shafts 61, 63 project along the device axialdirection 1 a and are attached to the fourth ring-shaped member 60 byfastening bolts 7. On the other hand, the planet shafts 62, 64 of twoplanet gears 6-2, 6-4 are formed of cylindrical collars 65 that arefixed between the second and fourth ring-shaped members 20, 60 byfastening bolts 8. One end 65 a of each cylindrical collar 65 isinserted into a slightly larger through-hole 67 formed in the fourthring-shaped member 60, and is able to move slightly in thecircumferential direction relative to the fourth ring-shaped member 60.Accordingly, when the four planet gears 6-1 to 6-4 are fixed to thefourth ring-shaped member 60, by rotating the other two planet gears 6-2and 6-4 slightly in the circumferential direction relative to the twoplanet gears 6-1, 6-3 that are tentatively attached, backlash adjustmentcan be performed for the engaging parts of the gears before thefastening bolts are properly tightened.

In the planetary gear device 1 with the construction described above,the sun gear 4 is usually used as a high-speed rotation input element.One of the internal gear 2 and the second ring-shaped member 20 used asthe carrier is usually set as a fixed element with the other being setas a reduced-speed rotation output element. All of these members areconcentrically aligned in the radial direction about the device axis 1a, so that a planetary gear device that is extremely slim in the deviceaxial direction 1 a can be realized.

By using hollow members as the first ring-shaped member 10 and the sungear 4 that are disposed on the very inside as in the presentembodiment, there is an advantage in that a hollow-type planetary geardevice can be easily realized.

On one side in the device axial direction, the end surfaces of the firstring-shaped member 10 that integrally rotates with the sun gear 4, thesecond ring-shaped member 20 that functions as the carrier of the planetgears, and the third ring-shaped member 30 that integrally rotates withthe internal gear 2 are all exposed. On the other side, the end surfacesof the sun gear 4, the fourth ring-shaped member 60 that integrallyrotates with the carrier of the planet gears, and the internal gear 2are exposed. Accordingly, another members can be connected to therespective rotating parts on either side in the device axial direction.This means that there is an advantage that the input and output can beeasily made from either side.

Modification of the First Embodiment

Here, in order to reduce the number of components in the above exampleand simplify and reduce the cost of the assembly process for the device,the first ring-shaped member 10 and the sun gear 4 may be formed of asingle member.

FIGS. 2A, 2B and 2C are a cross-sectional view, a left end view, and aright end view showing a modification of the planetary gear device ofthe first embodiment with the construction described above. Thefundamental structure of the planetary gear device 1A is the same asthat of the planetary gear device 1, so that corresponding parts aregiven the same reference numerals and description thereof will beomitted.

In the planetary gear device 1A of the present modification, the firstring-shaped member 10 and the sun gear 4 are formed of a singlering-shaped member 10A. An inner ring-side raceway groove 41A of thefirst cross roller bearing 40 is formed in an outer circumferentialsurface part 11B of the circular outer circumferential surface of thering-shaped member 10A on one side in the device axial direction, whileon the other side, external teeth 4A that compose the sun gear 4 areformed in an outer circumferential surface part 11C.

It should be noted that in addition to the above structure, or separateto the above structure, FIG. 4 illustrates that the third ring-shapedmember 30 and the internal gear 2 may also be formed of a singlering-shaped member 30A. In this case, the outer ring-side raceway groove52 of the second cross roller bearing 50 may be formed in an innercircumferential surface part of the circular inner circumferentialsurface of this ring-shaped member on one side in the device axialdirection, while on the other side, the internal teeth that compose theinternal gear 2 may be formed in an inner circumferential surface part.

In each of the examples described above, a central hollow 9 that passesthrough the center of the device is formed by the sun gear 4 and thefirst ring-shaped member 10. As an alternative, a solid cylindricalmember or a solid disc-shaped member may be used as the sun gear 4 andthe first ring-shaped member 10.

Second Embodiment

FIGS. 3A, 3B and 3C are a cross-sectional view, a left end view, and aright end view showing a two-stage planetary gear device that isconstituted by the planetary gear device 1 of the first embodiment. Thetwo-stage planetary gear device 100 includes a front stage-sideplanetary gear mechanism 110 and a rear stage-side planetary gearmechanism 120. The rear stage-side planetary gear mechanism 120 hassubstantially the same construction as the planetary gear device 1 ofthe first embodiment. Accordingly, the corresponding parts are given thesame reference numerals and description thereof will be omitted.

In the two-stage planetary gear device 100 of the present embodiment, acentral rotational shaft 70 (the fifth member) is concentricallydisposed rotatably on the inside of a circular inner circumferentialsurface 13 of the first ring-shaped member 10 in the rear stageplanetary gear mechanism 120. This central rotational shaft 70 iscomposed of a large-diameter disc-shaped part 71, a small-diameter inputshaft part 72 that coaxially projects from one end surface of thedisc-shaped part 71, and a small-diameter pinion shaft part 73 thatconcentrically projects from the opposite end surface of the disc-shapedpart 71.

A third cross roller bearing 80 is formed between a circular outercircumferential surface 74 of the disc-shaped part 71 and the circularinner circumferential surface 13 of the first ring-shaped member 10.More specifically, the third cross roller bearing 80 includes an innerring-side raceway groove 81 that is formed in the circular outercircumferential surface 74 of the disc-shaped part 71, an outerring-side raceway groove 82 that is formed in the circular innercircumferential surface 13 of the first ring-shaped member 10, and aplurality of rollers 83 that are inserted into a ring-shaped racewayformed between the circular outer circumferential surface 74 and thecircular inner circumferential surface 13 so that the rotational axes ofalternating rollers are perpendicular to one another.

The front stage-side planetary gear mechanism 110 includes a frontstage-side sun gear 111 formed in a front end part of the pinion shaft73, a plurality of front stage-side planet gears 112 disposed on theoutside of the front stage-side sun gear 111, and a front stage-sideinternal gear 113 formed in a circular inner circumferential surface ofthe sun gear 4 of the rear stage-side that surrounds these frontstage-side planet gears 112 to the outside. Planet shafts 114 of thefront stage-side planet gears 112 are supported in a cantilevered mannerby the fourth ring-shaped member 60. Further, FIG. 5 illustrates thefirst ring-shaped member 10 and the sun gear 4 formed from a singlemember 10B having a ring shaped or columnar shape.

It should be noted that in the present embodiment, the input shaft part72, the disc-shaped part 71 for forming the inner ring of a cross rollerbearing, and the pinion shaft part 73 in which the front stage-side sungear 111 is formed are all formed of a single member, though these partsmay be formed of separate members that are coaxially fixed together.

As shown in the drawings, in the two-stage planetary gear device 100constructed above, the carrier in each stage is usually set as a fixedelement, with the internal gear 2 of the rear stage-side planetary gearmechanism 120 being set as the reduced-speed rotation output element.The high-speed rotation inputted from the input shaft part 72 istransmitted via the front stage-side planetary gear mechanism 110 to therear stage-side planetary gear mechanism 120 and is obtained as areduced-speed rotation output from the internal gear 2 of the rearstage-side planetary gear mechanism 120.

In the two-stage planetary gear device 100 of the present embodimentalso, each gear part is concentrically arranged on a plane that isperpendicular to the device axis 100 a. Accordingly, a two-stageplanetary gear device that is extremely slim in the device axialdirection can be realized.

Also, since each gear of each stage can be accessed from both sides inthe device axial direction, there is a further advantage in that it isextremely easy to lay out the input and output.

INDUSTRIAL APPLICABILITY

As described above, the planetary gear device of the present inventionis constituted so that the sun gear, the internal gear, the carrier forsupporting the planet gears, and two cross roller bearings forsupporting these elements in a manner that they are rotatable relativeto one another are concentrically arranged on a plane perpendicular tothe device axis. Accordingly, with the present invention, a planetarygear device that is extremely slim in the device axial direction can berealized.

Also, according to the present invention, the sun gear, the carrier forsupporting the planet gears, and the internal gear can be accessed fromboth sides in the device axial direction, so that there is the advantagein that the input and output of the device can be freely laid out, whichmakes the device extremely easy to design.

In addition, there is the advantage that by using hollow members as thesun gear that is disposed on the very inside and the members that areconnected to the sun gear, it is easy to realize a hollow-type planetarygear device.

In a two-stage planetary gear device according to the present invention,the front stage-side planetary gear mechanism is incorporatedconcentrically with the center of the rear stage-side planetary gearmechanism. The cross roller bearing for rotatably supporting the sungear is also incorporated concentrically with the center of the rearstage-side planetary gear mechanism. Accordingly, with the presentinvention, a two-stage planetary gear device that is extremely slim inthe device axial direction can be realized.

1. A planetary gear device comprising: a ring-shaped or columnar firstmember having a circular outer circumferential surface; a secondring-shaped member disposed concentrically so as to surround thecircular outer circumferential surface of the first member; a thirdring-shaped member disposed concentrically so as to surround a circularouter circumferential surface of the second ring-shaped member; aninternal gear coaxially attached to one ring-shaped end surface of thethird ring-shaped member; a sun gear coaxially attached to an endsurface, which is circular or ring-shaped, of the first member; aplurality of planet gears that are attached to a ring-shaped end surfaceof the second ring-shaped member and engage with the internal gear andthe sun gear; a first bearing formed between the circular outercircumferential surface of the first member and a circular innercircumferential surface of the second ring-shaped member; and a secondbearing formed between a circular outer circumferential surface of thesecond ring-shaped member and a circular inner circumferential surfaceof the third ring-shaped member, wherein the first member and the sungear are formed from a single member having a ring shape or columnarshape, and an inner ring-side raceway groove of the first bearing isformed in an outer circumferential surface part of a circular outercircumferential surface of the single member on one side in a deviceaxial direction, and external teeth that compose the sun gear are formedin an outer circumferential surface part on the other side of the singlemember.
 2. A planetary gear device according to claim 1, wherein atleast one of the first bearing and the second bearing is a cross rollerbearing.
 3. A planetary gear device comprising: a ring-shaped orcolumnar first member having a circular outer circumferential surface; asecond ring-shaped member disposed concentrically so as to surround thecircular outer circumferential surface of the first member; a thirdring-shaped member disposed concentrically so as to surround a circularouter circumferential surface of the second ring-shaped member; aninternal gear coaxially attached to one ring-shaped end surface of thethird ring-shaped member; a sun gear coaxially attached to an endsurface, which is circular or ring-shaped, of the first member; aplurality of planet gears that are attached to a ring-shaped end surfaceof the second ring-shaped member and engage with the internal gear andthe sun gear; a first bearing formed between the circular outercircumferential surface of the first member and a circular innercircumferential surface of the second ring-shaped member; and a secondbearing formed between a circular outer circumferential surface of thesecond ring-shaped member and a circular inner circumferential surfaceof the third ring-shaped member, wherein the third ring-shaped memberand the internal gear are formed from a single ring-shaped member, andan outer ring-side raceway groove of the second bearing is formed in aninner circumferential surface part of a circular inner circumferentialsurface of the single ring-shaped member on one side in the device axialdirection, and internal teeth that compose the internal gear are formedin an inner circumferential surface part on the other side of the singlering-shaped member.
 4. A planetary gear device according to claim 1,further comprising a fourth ring-shaped member that supports the planetgears from an opposite side to the second ring-shaped member in thedevice axial direction, wherein the planet gears include four planetgears that are disposed at intervals of an equal angle, and planetshafts of two planet gears disposed at an interval of 180 degrees aresupported between the second ring-shaped member and the fourthring-shaped member so that an angular position in a circumferentialdirection relative to planet shafts of two other planet gears, out ofthe four planet gears, that are also disposed at an interval of 180degrees can be adjusted.
 5. A planetary gear device according to claim3, wherein at least one of the first bearing and the second bearing is across roller bearing.
 6. A planetary gear device according to claim 3,further comprising a fourth ring-shaped member that supports the planetgears from an opposite side to the second ring-shaped member in thedevice axial direction, wherein the planet gears include four planetgears that are disposed at intervals of an equal angle, and planetshafts of two planet gears disposed at an interval of 180 degrees aresupported between the second ring-shaped member and the fourthring-shaped member so that an angular position in a circumferentialdirection relative to planet shafts of two other planet gears, out ofthe four planet gears, that are also disposed at an interval of 180degrees can be adjusted.
 7. A planetary gear device comprising: aring-shaped or columnar first member having a circular outercircumferential surface; a second ring-shaped member disposedconcentrically so as to surround the circular outer circumferentialsurface of the first member; a third ring-shaped member disposedconcentrically so as to surround a circular outer circumferentialsurface of the second ring-shaped member; an internal gear coaxiallyattached to one ring-shaped end surface of the third ring-shaped member;a sun gear coaxially attached to an end surface, which is circular orring-shaped, of the first member; a plurality of planet gears that areattached to a ring-shaped end surface of the second ring-shaped memberand engage with the internal gear and the sun gear; a first bearingformed between the circular outer circumferential surface of the firstmember and a circular inner circumferential surface of the secondring-shaped member; and a second bearing formed between a circular outercircumferential surface of the second ring-shaped member and a circularinner circumferential surface of the third ring-shaped member, whereinthe first member and the sun gear are ring-shaped members, a fifthmember that has a circular outer circumferential surface isconcentrically disposed inside a circular inner circumferential surfaceof the first member, a front stage-side internal gear is formed in acircular inner circumferential surface of the sun gear, a frontstage-side sun gear is coaxially attached to one end surface of thefifth member in the device axial direction, a plurality of frontstage-side planet gears engaged with the front stage-side internal gearand with the front stage-side sun gear are disposed between the frontstage-side internal gear and the front stage-side sun gear, and a thirdbearing is formed between the circular outer circumferential surface ofthe fifth member and the circular inner circumferential surface of thefirst member.
 8. A planetary gear device according to claim 7, whereinat least one of the first bearing, the second bearing, and the thirdbearing is a cross roller bearing.
 9. A planetary gear device accordingto claim 8, wherein a central rotational shaft is coaxially attached toanother end surface of the fifth member in the device axial direction.10. A planetary gear device according to claim 9, wherein the fifthmember, the central rotational shaft, and the front stage-side sun gearare formed from a single member.
 11. An planetary gear device accordingto claim 7, wherein the first member and the sun gear are formed from asingle member having a ring shaped or columnar shape, and an innerring-side raceway groove of the first bearing is formed in an outercircumferential surface part of a circular outer circumferential surfaceof the single member on one side in the device axial direction, andexternal teeth that compose the sun gear are formed in an outercircumferential surface part on another side of the single member.
 12. Aplanetary gear device according to claim 7, wherein the thirdring-shaped member and the internal gear are formed from a singlering-shaped member, and an outer ring-side raceway groove of the secondbearing is formed in an inner circumferential surface part of a circularinner circumferential surface of the single ring-shaped member on oneside in the device axial direction, and internal teeth that compose theinternal gear are formed in an inner circumferential surface part onanother side of the single ring-shaped member.
 13. A planetary geardevice according to claim 7, further comprising a fourth ring-shapedmember that supports the planet gears from an opposite side to thesecond ring-shaped member in the device axial direction, wherein theplanet gears include four planet gears that are disposed at intervals ofan equal angle, and planet shafts of two planet gears that are disposedat an interval of 180 degrees are supported between the secondring-shaped member and the fourth ring-shaped member so that an angularposition in a circumferential direction relative to planet shafts of twoother planet gears disposed at an interval of 180 degrees, can beadjusted.